ductwork question - http://www.hvacmechanic.com/ Forums
Original message
| Mark19960
 |  "ductwork question"
, posted Sun 27 Apr 12:28  
just over a year ago we bought our house.
About 2-3 months after we moved in I noticed that on really hot days our system seemed to have a tough time cooling the house.
Along with that the line that drained water on the outside of the house used to literally pour water.
It was like someone was running a faucet in there.
Then in the winter we had issues with it not heating very well on cold nights.
Called 2 different services out and they never found any real issue and one of my complaints was that I felt cold air coming out of the return duct where we put the filter.
I told them that I suspected a problem with the ductwork especially with the water in the summer and that now in the winter the air seemed to have an odor.
I myself went under the house looking for holes with one guy and we crawled the whole length of tubing and never found a hole in it.
about 4-5 weeks ago I went under the house for something unrelated and the unit came on while I was under there.. and I found myself in a wind tunnel - I had found the hole in the ductwork.
The duct goes into the floor but what they did was secured a piece of sheet metal to the underside of the floor and used a portion of the space between the floor and the plate as a duct.
They never sealed one end of it..... so we had air from the crawlspace being sucked into the system...
Overall, not a good thing.
So, the next day I got someone to help me and we took that section of duct out, went to a hvac supply and got the same size duct just made out of newer flexible material and replaced it.
The old duct was full of dust and dirt.
I also cleaned the coil on the inside of the air handler which was loaded with dust as was the blower.
the ductwork out of the unit was not nearly as bad, seemed to be confined to the other side of the coil and that duct that we got a new section and replaced.
We patched the hole with 2 pieces of wood, caulked around them to seal the cracks and made sure the insulation under the floor was put back neatly around it.
So, now the issue that I seem to be having is that section of sheet metal they secured under the floor to use as a duct was really to bypass a restriction, since the supply to the vents in the rooms was just as big as the return and they had to cross path, basically.
That sheet metal.. whenever the unit comes on, it pops loudly.
I thought about going under there and simply propping it up with a piece of wood or something but then realized that there must be significant vacuum there to cause the sheet metal to actually do that, I could do it by pushing on it with my hand but it was not light pressure - I had to put some effort into it.
The return where we put our air filter takes a filter size that is 20x25x1
if I take the filter off this metal popping seems to stop or not happen so much or as loud so the filter adds enough restriction there to cause that to happen.
The thing is, there are 2 pieces of sheet metal screwed into the sides of this return to make it accept 20x25x1
the opening, if I removed the sheet metal that was placed inside of there is actually 20x30x1
Since I repaired the hole in the duct under the house the difference is night and day.
We had some cold nights in the week following the patched hole and replaced duct and the smell is gone, the unit works much better and our electric bill dropped off significantly.
Should I remove the 2 pieces of thin sheet metal and use the larger filter?
Thing is, we have to get filters with like a metal mesh on the back because one filter.. disintegrated and I had to fish pieces of it out of the blower motor. :(
Or, is the fan speed too high?
Anything I guess is a possibility, since whoever put this in was not careful.
Anything else I should look out for?
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Replies:
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| Jojo98
| "Re(1):ductwork question" , posted Tue 29 Apr 13:28
Get a reputable HVAC company to redesign and install your ductwork, and be done with it.
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| Houston204
| "Re(1):ductwork question" , posted Sun 27 Apr 13:33
I would find some 20x30 filters and remove the sheet metal.
"Tip of the Day" Remember to remove power first.
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| | dwcaveney
| "What size unit? Those darn skunks!" , posted Tue 29 Apr 06:17:
What are the specs for the unit: CFM, BTU, Cooling (tons)? Any other system information? What is your climate zone? (IOWs, where do you live?)
I assume for cooling you are using 400CFM/200BTUM to equal a ton? (12000BTU/60 minutes). Any difference in pop noise, heat versus cool? What size is the return duct?
What is the volume of the sealed space, where the popping occurs, relative to the return duct?
Does the R/A plenum "pop"?
A pop, indicates you have a SIGNIFICANT restriction/undersized return air.
A restriction or undersizing effects the TEL (total effective length)of an air delivery system. The fan will not load properly without sufficient return air.
The up-size filter will help. I would consider adding more R/A.(rework the restriction or add another filter rack, then duct to the R/P)
I took a PG&E duct class (Manual D and T). Heard a story about a guy, undersizing R/A duct, then "fixing" it with a "dirty" make-up air intake (opening the R/A duct to an unconditioned zone).
Do you think the skunks caused the problem?
DW
[this message was edited by dwcaveney on Tue 29 Apr 10:13] |
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